The company that constructed the Tappan Zee Bridge six decades ago will be part of the team that builds its $4 billion replacement, one of the largest public works projects in the nation.

More than a decade after talk of a new bridge first started, seven members of the New York Thruway Authority, which owns the 3-mile bridge, unanimously selected Tappan Zee Constructors this afternoon to design and build a new twin-span crossing across the Hudson River.

The $3.1 billion construction contract is one of the largest in state history. The full cost of the project will approach $4 billion after $500- to $800 million environmental mitigation, management and financial costs are added. That still puts the project significantly well below the state’s original $5 billion estimate.

Pennsylvania-based American Bridge Company, which built the existing Tappan Zee in the 1950s, partnered with Texas-based Fluor Enterprise and others as Tappan Zee Contractors to win the contract against two other consortiums bidding on the project.

Tappan Zee Constructors contends it can build a twin-span cable-stayed bridge — with its angled towers resembling tuning forks — in little more than five years for $3.1 billion. As part of a new law specially created for the project, the design-builders will be financially responsible for cost overruns and delays.

The two other bidders — one from a joint venture involving Kiewit Infrastructure and Skanska USA ($4 billion) and a second from a Bechtel Infrastructure and Tutor Perini partnership ($3.9 billion) — each needed closer to six years to build the bridge and required more dredging.

Both the state Attorney General and Comptroller must still review the contract. Construction is expected to begin next year.